Synalpheus carinatus

Synalpheus carinatus (de Man, 1888)

(Figs 3a, b, c, 4a)

Restricted synonymy:

Alpheus carinatus de Man, 1888: 508, pl. 22, fig. 2.

Synalpheus carinatus de Man, 1911: 210, pl. 6, fig. 23; Banner & Banner, 1968: 272; Banner & Banner, 1975: 283–285, fig. 1, 2n.

Nec Synalpheus carinatus Pearson, 1905: 83, pl. 2, figs 9 (= S. trispinosus de Man).

Material examined. Four specimens: Two ovigerous females (cl 7.8 mm and 8.3 mm, tl 26 mm and 27.4 mm), India, Lakshadweep, Amini Island, 11°07.739’N 72°44.119’E, depth 10m, on Phanogenia gracilis, 17 February 2018 (C8017/2 and C8018/2).

Two females(cl 5.4 mm and 4.7mm,tl 18.2 mm and 19.2 mm), India, Lakshadweep,Kavaratti Island, 10°32.256’N 72°37.083’E, depth 15m, on Phanogenia multibrachiata, 10 February 2018 (ZSI/ Crustacea /C8028/2 and ZSI/ Crustacea /C8029/2).

Short Description. Rostrum concave in lateral view, overreaching distal portion of the second article of antennular region, rostrum and carapace bearing strong median carina. Carina compressed, knife-like in the anterior cardiac region. Carapace with a humped profile. Orbital teeth tilting upward above the rostrum, rostral and orbital carinae depressed into moderate deep grooves in the anterior region. Pterygostomial region subacute and not projecting. First antennular segment longer than the second and third segments. Stylocerite reaching to the middle of the second article of antennular peduncle. Scaphocerite lateral spines are prominent and slightly reaching the distal portion of the third article of antennular peduncle. Large chela compressed, superior margin of carpus with two distal spines and inferior margin with one acute spine. Merus infero-internal margin terminating in sharp angle, superior margin projecting into an acute tooth. Superior margin of ischium with short heavy spine. Small chela dactylus straight, armature of merus, carpus and ischium like large chela. Last three pereiopods with dactylus biunguiculate, superior unguis is longer than the inferior, propodus bearing spines on the lower margin, 1.06 times longer than the merus. Merus almost equal to propodus and unarmed. Abdominal pleura with last three segments bearing acute spine on the lateral tip. Telson broad posteriorly, dorsal spines located posterior of middle region and posterior region convex.

Coloration. Entire carapace, rostrum, abdominal segments and pereiopods brown to dark brown. Pleopods brownish orange. Telson light brown, uropods dark brown.

Distribution. Indo-Pacific: Indonesia, China, Thailand, Malaysian Archipelago, Australia, Marshall and Gilbert Islands (Banner & Banner 1966b, 1975, Chace 1988, Wang & Sha, 2015). Now from India (Lakshadweep).

Host. Commonly associated with crinoids. In the present study, S. carinatus was associated with Phanogenia gracilis and P. multibranchiata.

Remarks. S. carinatus can be easily distinguished from its related congeners S. comatularum by its rostral carina that is extending to the posterior margin of carapace, rostrum concave in lateral view, orbital teeth extending upward beyond the rostrum in lateral view. Pearson (1905) reported the species from the Gulf of Mannar, Ceylon, however, Banner and Banner (1975) believe that the species to be S. trispinosus based on the presence of three spines on the posterior region of sixth abdominal somite which is absent S. carinatus.